Overview

Plague is a serious bacterial infection that's transmitted by fleas. Known as the Black Death during medieval times, today plague occurs in fewer than 5,000 people a year worldwide. It can be deadly if not treated promptly with antibiotics.

The organism that causes plague, Yersinia pestis, lives in small rodents found most commonly in rural and semirural areas of Africa, Asia and the United States. The organism is transmitted to humans who are bitten by fleas that have fed on infected rodents or by humans handling infected animals.

The most common form of plague results in swollen and tender lymph nodes — called buboes — in the groin, armpits or neck. The rarest and deadliest form of plague affects the lungs, and it can be spread from person to person.

Symptoms

Plague is divided into three main types — bubonic, septicemic and pneumonic — depending on which part of your body is involved. Signs and symptoms vary depending on the type of plague.

Bubonic plague

Bubonic plague is the most common variety of the disease. It's named after the buboes — swollen lymph nodes — which typically develop within a week after an infected flea bites you. Buboes may be:

Situated in the groin, armpit or neck

About the size of a chicken egg

Tender and warm to the touch

Other signs and symptoms may include:

Sudden onset of fever and chills

Headache

Fatigue or malaise

Muscle aches

Pneumonic plague

Pneumonic plague affects the lungs. It's the least common variety of plague but the most dangerous, because it can be spread from person to person via cough droplets. Signs and symptoms can begin within a few hours after infection, and may include:

Cough, with bloody sputum

Difficulty breathing

Nausea and vomiting

High fever

Headache

Weakness

Pneumonic plague progresses rapidly and may cause respiratory failure and shock within two days of infection. If antibiotic treatment isn't initiated within a day after signs and symptoms first appear, the infection is likely to be fatal.

When to see a doctor

Seek immediate medical attention if you begin to feel ill and have been in an area where plague has been known to occur. This includes parts of several states in the western portion of the United States — primarily New Mexico, Arizona, California and Colorado.

Causes

The plague bacteria, Yersinia pestis, is transmitted to humans when they are bitten by fleas that have previously fed on infected animals, such as:

Rats

Squirrels

Rabbits

Prairie dogs

Chipmunks

The bacteria can also enter your body if you have a break in your skin that comes into contact with an infected animal's blood. Domestic cats and dogs can become infected with plague from flea bites or from eating infected rodents.

Pneumonic plague, which affects the lungs, is spread by inhaling infectious droplets coughed into the air by a sick animal or person.

Risk factors

The risk of developing plague is very low. Worldwide, only a few thousand people develop plague each year. However, your risk of plague can be increased by where you live and travel, your occupation, and even by some of your hobbies.

Location

Plague outbreaks are most common in rural and semirural areas characterized by overcrowding, poor sanitation and a high rodent population. The greatest number of human plague infections occurs in Africa.

Occupation

Veterinarians and their assistants have a higher risk of coming into contact with domestic cats and dogs that may have become infected with plague. Also at higher risk are people who work outdoors in areas where plague-infected animals are common.

Hobbies

Camping, hunting or hiking in areas where plague-infected animals reside can increase your risk of being bitten by an infected flea.

Complications

Complications of plague may include:

Death. Most people who receive prompt antibiotic treatment survive bubonic plague. Untreated plague has a high fatality rate.

Gangrene. Blood clots in the tiny blood vessels of your fingers and toes can disrupt the flow of blood and cause that tissue to die. The portions of your fingers and toes that have died may need to be amputated.

Prevention

Although no effective vaccine is available, scientists are working to develop one. Antibiotics can help prevent infection if you're at risk of or have been exposed to plague. Take the following precautions if you live or spend time in regions where plague outbreaks occur:

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